signal vs unknown

signal

noun
  • Useful information, as opposed to noise. 

  • A token; an indication; a foreshadowing; a sign. 

  • A signalling interaction between cells 

  • An electromagnetic action, normally a voltage that is a function of time, that conveys the information of the radio or TV program or of communication with another party. 

  • Any variation of a quantity or change in an entity over time that conveys information upon detection. 

  • An on-off light, semaphore, or other device used to give an indication to another person. 

  • A simple interprocess communication used to notify a process or thread of an occurrence. 

  • An action, change or process done to convey information and thus reduce uncertainty. 

  • A sign made to give notice of some occurrence, command, or danger, or to indicate the start of a concerted action. 

  • A sequence of states representing an encoded message in a communication channel. 

verb
  • To communicate with (a person or system) by a signal. 

  • To indicate; to convey or communicate by a signal. 

adj
  • Standing above others in rank, importance, or achievement. 

unknown

noun
  • Any thing, place, or situation about which nothing is known; an unknown fact or piece of information. 

  • A variable (usually x, y or z) whose value is to be found. 

  • A person of no identity; a nonentity 

adj
  • Not known; unidentified; not well known. 

How often have the words signal and unknown occurred in a corpus of books? (source: Google Ngram Viewer )